OFFSET
0,1
FORMULA
Lim sup n->infinity (|a(n)|/(4*n)!)^(1/(4*n)) = 0.9003163161571... = abs(1/r), where r is the complex root of the equation sin(r)*(exp(2*r)-1) = I*cos(r)*(exp(2*r)+1). - Vaclav Kotesovec, Nov 02 2013
MATHEMATICA
With[{nn=30}, Take[CoefficientList[Series[ArcSinh[Tanh[x]Tan[x]], {x, 0, nn}], x] Range[0, nn]!, {3, -1, 4}]] (* Harvey P. Dale, Aug 08 2013 *)
CROSSREFS
KEYWORD
sign
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
STATUS
approved